Apparatus and method for optionally using secondary frequency assignment in a wireless communication system using multiple bands

ABSTRACT

Methods for operating a Base Station (BS) and a User Equipment (UE) in a wireless communication system using a primary frequency and one or more secondary frequencies, and apparatuses for the BS and UE for carry out the methods, are provided. The method for operating the BS includes determining whether to activate or deactivate at least one of the one or more secondary frequencies, and transmitting a message comprising a bitmap indicating the activation or deactivation of the at least one of the one or more secondary frequencies to the UE. The method for operating the UE includes receiving a message comprising a bitmap indicating activation or deactivation of at least one of the one or more secondary frequencies from the BS, and activating or deactivating the at least one of the one or more secondary frequencies based on the received message.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/927,577, filed Mar. 21, 2018 (pending), which is a continuation ofprior U.S. patent application Ser. No. 13/420,020, filed Mar. 14, 2012,which is a continuation of U.S. patent application Ser. No. 12/542,175,filed Aug. 17, 2009. now U.S. Pat. No. 8,149,777, which claims thebenefit under 35 U.S.C. .sctn. 119(a) of a Korean patent applicationfiled in the Korean Intellectual Property Office on Aug. 18, 2008 andassigned Serial No. 10-2008-0080356 and a Korean patent applicationfiled in the Korean Intellectual Property Office on May 27, 2009 andassigned Serial No. 10-2009-0046676, the entire disclosures of each ofwhich are hereby incorporated by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a broadband wireless communicationsystem using multiple bands. More particularly, the present inventionrelates to an apparatus and a method for reducing power consumption of aMobile Station (MS) in the broadband wireless communication system usingthe multiple bands.

2. Description of the Related Art

In accordance with advances of wireless communication systems, varioustypes and high quality of services provided by the wirelesscommunication systems are demanded. To meet those demands, a broadbandwireless communication system is drawing attention. As availablefrequency resources in the wireless communication system are limited,available frequency bands in the broadband wireless communication systemare also limited. To offer a broadband service, the available frequencybands needs to increase.

FIGS. 1A and 1B are diagrams illustrating simplified structures forsupporting single frequency band and a simplified structure forsupporting two frequency bands in a conventional wireless communicationsystem.

In the wireless communication system, more particularly, in thebroadband wireless communication system represented by the Institute ofElectrical and Electronics Engineers (IEEE) 802.16 standard, a BaseStation (BS) operates one Frequency Assignment (FA) or two or more FAs.The BS offers a radio communication service to a Mobile Station (MS)through its FA.

Referring to FIG. 1A, an MS 100 may migrate from an FA1 region 120 to anFA2 region 140. Herein, the FA1 region 120 is a service coverage areawhere the MS 100 uses the radio communication service using an FA1, andthe FA2 region 140 is a service coverage area where the MS 100 uses theradio communication service using an FA2. When the MS 100 traveling inthe FA1 region 120 may operate only one FA or when the FA1 and the FA2are managed by different BSs, the MS 100 hands over between the FAs anduses the radio communication service using the FA2.

Referring to FIG. 1B, when an MS 150 may operate two or more FAs or whentwo or more FAs are managed by the single BS, the MS 150 may use theradio communication service in both of the FA1 region 160 and the FA2region 180. As such, when transmitting and receiving signals over themultiple frequency bands, the MS and the BS may send mass data at a highdata rate.

As discussed above, by use of the multiple frequency bands at the sametime, the system may offer the high-capacity services at a high datarate. However, currently, there is no band use control procedure foreffective utilization of the multiple frequency bands. As a result, itis not possible to regulate the bands adaptively used based on aresource usage rate and a channel condition, and use of a secondary FAincreases power consumption of the MS.

SUMMARY OF THE INVENTION

An aspect of the present invention is to address at least the abovementioned problems and/or disadvantages and to provide at least theadvantages described below. Accordingly, an aspect of the presentinvention is to provide an apparatus and a method for efficiently usingmultiple frequency bands between a Mobile Station (MS) and a BaseStation (BS) in a broadband wireless communication system.

Another aspect of the present invention is to provide an apparatus and amethod for regulating Frequency Assignments (FAs) optionally usedaccording to a resource utilization rate and a channel condition in abroadband wireless communication system.

Yet another aspect of the present invention is to provide an apparatusand a method for reducing power consumption in using secondary FAs in abroadband wireless communication system.

Still another aspect of the present invention is to provide an apparatusand a method for suspending use of a secondary FA in a broadbandwireless communication system.

A further aspect of the present invention is to provide an apparatus anda method for resuming use of a suspended secondary FA in a broadbandwireless communication system.

According to an aspect of the present invention, a method for operatinga BS in a wireless communication system using a primary frequency andone or more secondary frequencies is provided. The method includesdetermining whether to activate or deactivate at least one of the one ormore secondary frequencies, and transmitting a message comprising abitmap indicating the activation or deactivation of the at least one ofthe one or more secondary frequencies to a User Equipment (UE).

According to another aspect of the present invention, a method foroperating a UE in a wireless communication system using a primaryfrequency and one or more secondary frequencies is provided. The methodincludes receiving a message comprising a bitmap indicating activationor deactivation of at least one of the one or more secondary frequenciesfrom a BS, and activating or deactivating the at least one of the one ormore secondary frequencies based on the received message.

According to yet another aspect of the present invention, an apparatusfor a BS in a wireless communication system using a primary frequencyand one or more secondary frequencies is provided. The apparatusincludes a controller configured to determine whether to activate ordeactivate at least one of the one or more secondary frequencies, and atransmitter configured to transmit a message comprising a bitmapindicating the activation or deactivation of the at least one of the oneor more secondary frequencies to a UE.

According to still another aspect of the present invention, an apparatusfor a UE in a wireless communication system using a primary frequencyand one or more secondary frequencies is provided. The apparatusincludes a receiver configured to receive a me sage comprising a bitmapindicating activation or deactivation of at least one of the one or moresecondary frequencies from a BS, and a controller configured to activateor deactivate the at least one of the one or more secondary frequenciesbased on the received message.

Other aspects, advantages, and salient features of the invention willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses exemplary embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainexemplary embodiments of the present invention will be more apparentfrom the following description taken in conjunction with theaccompanying drawings, in which:

FIGS. 1A and 1B are diagrams illustrating simplified structuresaccording to a number of Frequency Assignments (FAs) supported in awireless communication system;

FIG. 2 is a diagram illustrating signal exchanges for Secondary (S)-FAon-off in a broadband wireless communication system according to anexemplary embodiment of the present invention;

FIG. 3 is a diagram illustrating signal exchanges for S-FA on-off in abroadband wireless communication system according to an exemplaryembodiment of the present invention;

FIG. 4 is a diagram illustrating signal exchanges for S-FA on-off in abroadband wireless communication system according to an exemplaryembodiment of the present invention;

FIG. 5 is a diagram illustrating signal exchanges for S-FA on-off in abroadband wireless communication system according to an exemplaryembodiment of the present invention;

FIG. 6 is a diagram illustrating signal exchanges for S-FA on-off in abroadband wireless communication system according to an exemplaryembodiment of the present invention;

FIG. 7 is a diagram illustrating signal exchanges for S-FA on-off in abroadband wireless communication system according to an exemplaryembodiment of the present invention;

FIG. 8 is a flowchart illustrating operations of a Mobile Station (MS)in a broadband wireless communication system according to an exemplaryembodiment of the present invention;

FIG. 9 is a flowchart illustrating operations of a Base Station (BS) ina broadband wireless communication system according to an exemplaryembodiment of the present invention;

FIG. 10 is a flowchart illustrating operations of a BS in a broadbandwireless communication system according to an exemplary embodiment ofthe present invention;

FIG. 11 is a flowchart illustrating operations of an MS in a broadbandwireless communication system according to an exemplary embodiment ofthe present invention;

FIG. 12 is a block diagram illustrating an MS in a wirelesscommunication system according to an exemplary embodiment of the presentinvention; and

FIG. 13 is a block diagram illustrating a BS in a wireless communicationsystem according to an exemplary embodiment of the present invention.

Throughout the drawings, like reference numerals will be understood torefer to like parts, components and structures.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of exemplaryembodiments of the invention as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the embodiments described hereinmay be made without departing from the scope and spirit of theinvention. Also, descriptions of well-known functions and constructionsare omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of theinvention. Accordingly, it should be apparent to those skilled in theart that the following description of exemplary embodiments of thepresent invention are provided for illustration purpose only and not forthe purpose of limiting the invention as defined by the appended claimsand their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

By the term “substantially” it is meant that the recited characteristic,parameter, or value need not be achieved exactly, but that deviations orvariations, including for example, tolerances, measurement error,measurement accuracy limitations and other factors known to those ofskill in the art, may occur in amounts that do not preclude the effectthe characteristic was intended to provide.

Exemplary embodiments of the present invention provide a technique forminimizing power consumption in using secondary Frequency Assignment(FA) in a broadband wireless communication system using multiple bands.Hereinafter, Orthogonal Frequency Division Multiplexing(OFDM)/Orthogonal Frequency Division Multiple Access (OFDMA) wirelesscommunication system is illustrated by way of example. Note that thepresent invention is applicable to other wireless communication systems.

Hereinafter, a mode for transmitting and receiving signals between aMobile Station (MS) and a Base Station (BS) through multiple FAs isreferred to as an overlay mode. The term “MS” may also be referred to as“User Equipment (UE).” A wireless communication system operating in theoverlay mode is referred to as an overlay wireless communication system.

FIG. 2 is a diagram illustrating signal exchanges for secondary FAon-off in an overlay wireless communication system according to anexemplary embodiment of the present invention. In FIG. 2, an MS 200 anda BS 250 manage two frequency band, that is, a Primary (P)-FA 251 and aSecondary (S)-FA 253. Notably, the procedure of FIG. 2 is applicable toa system which manages three or more FAs, that is, one P-FA and two ormore S-FAs.

Referring to FIG. 2, the MS 200 transmits and receives data with the BS250 over its P-FA 201, and transmits and receives data with the BS 250over its S-FA 203 in step 211. Herein, the P-FA 201 is determined at aninitial connection of the MS 200. Accordingly, when a plurality of MSsexists, the P-FAs of the MSs may be allocated to different FAs. That is,the P-FA of a certain MS may be the S-FA of another MS.

In the process of the data communication, the MS 200 determines based onits battery status whether it needs to suspend use of the S-FA 203. Thesuspension of the S-FA 203 is determined based on a signal strengthmeasurement value of the S-FA 203 and power consumption. For example,when the signal strength measurement value of the corresponding S-FA isless than a threshold required for data delivery or when the remainingcapacity of the battery is insufficient to keep using the S-FA 203, theMS 200 determines to suspend the use of the S-FA 203.

Upon determining the suspension of the S-FA 203, the MS 200 sends anS-FA off request message to the BS 250 to request the suspension of theusage of the S-FA 203 in step 213. The S-FA off request message includesindication information of the S-FA 203 requested to suspend. Forexample, the indication information is one of frequency information ofthe S-FA 203, an index of the S-FA 203, and an S-FA bitmap representingthe S-FA 203. Herein, the index is a physical carrier index or a logicalcarrier index. The bitmap size is equal to a number of the S-FAsallocated to the MS 200. When the S-FAs allocated to the MS 200 aredifferent from the S-FAs actually used by the MS 200, the bitmap size isdetermined by the number of the S-FAs actually used by the MS 200 andindicates a particular S-FA to suspend among the S-FA actually used bythe MS 200. When the MS 200 is able to predict an off duration of theS-FA 203 by analyzing occurrence of uplink data, the MS 200 may addinformation indicative of the off duration of the S-FA 203 to the offrequest message. The information indicative of the off durationcontained in the off request message may be used for the BS 250 toperform data scheduling of the MS 200.

The BS 250, receiving the off request message from the MS 200, sends anS-FA off response message in reply to the off request message in step215. Herein, the S-FA off response message includes an indicatorindicative of the approval or disapproval of the use suspension requestof the S-FA 203. Accordingly, the MS 200 and the BS 250 recognize thesuspension of the S-FA 203 and transmit and receive data only over theP-FA 250 in step 217. When using two or more S-FAs in contrast to FIG.2, the MS 200 transmits and receives data over at least one S-FAexcluding the suspended S-FA 203 and the P-FA.

Next, if it is determined that the data transmission and reception withthe BS 250 is possible using the S-FA 203, the MS 200 ends an S-FAreadiness indicator to the BS 250 to inform the BS 250 of theavailability of the S-FA 203 in step 219. In so doing, the MS 200 mayperform a ranging procedure for the S-FA 203 if necessary.

Upon receiving the S-FA readiness indicator, the BS 250 determineswhether to allow the use resumption of the suspended S-FA and send anS-FA readiness indicator ACK to the MS 200 in step 221. Whether topermit the use resumption of the suspended S-FA is determined based onthe signal strength measurement value of the S-FA 203 reported by the MS200, the load of the S-FA 203, and the existence and the number of MSsusing the S-FA 203 as the P-FA. Hence, the S-FA readiness indicator ACKincludes one of information informing of the permission to transmit andreceive data over the S-FA 203 of the MS 200, information informing ofthe disapproval on the data delivery over the S-FA 203 of the MS 200,and information requesting to use other FA than the S-FA 203. When theuse of the S-FA 203 is not allowed, the BS 250 adds frequencyinformation or FA identification information of the other FAs to theS-FA readiness indicator ACK. At this time, it is assumed that the datatransfer over the S-FA 203 of the MS 200 is permitted.

Upon confirming the permission of the data transfer with the BS 250 overthe S-FA 203 from the S-FA readiness indicator ACK, the MS 200 transmitsand receives data with the BS 250 over the P-FA 201 and data with the BS250 over the S-FA 203 in step 223.

In FIG. 2, the MS sends a message for turning off the S-FA. Also, the MSmay request the entrance into a sleep mode and the use suspension of theS-FA together, which shall be described below in detail by referring toFIG. 3.

FIG. 3 is a diagram illustrating signal exchanges for S-FA on-off in anoverlay wireless communication system according to an exemplaryembodiment of the present invention.

Referring now to FIG. 3, an MS 300 transmits and receives data with a BS350 over the P-FA 301 and data with the BS 350 over the S-FA 303 in step311. Herein, the S-FA 301 is determined at the initial connection of theMS 300. When a plurality of MSs exists, the P-FAs of the MS may be setto different FAs. That is, the P-FA of a particular MS may be the S-FAof another MS.

The MS 300 determines to enter into the sleep mode and concurrentlydetermines to stop using the S-FA 303. The suspension of the S-FA 303 isdetermined based on a signal strength measurement value of the S-FA 303and power consumption. For example, when the signal strength measurementvalue of the corresponding S-FA is less than a threshold required forthe data delivery or when the remaining capacity of the battery isinsufficient to keep using the S-FA 303, the MS 300 determine to stopusing the S-FA 303.

The MS 300 sends a SLeeP (SLP)-REQuest (REQ) message including an S-FAoff request which requests to suspend the use of the S-FA 303, to the BS350 in step 313. The S-FA off request includes indication information ofthe S-FA 303 requested to stop. For example, the indication informationis one of the frequency information of the S-FA 303, the index of theS-FA 303, and the S-FA bitmap representing the S-FA 303. Herein, theindex is the physical carrier index or the logical carrier index. Thebitmap size is equal to the number of the S-FAs allocated to the MS 300.When the S-FAs allocated to the MS 300 differ from the S-FAs actuallyused by the MS 300, the bitmap size is determined according to thenumber of the S-FAs actually used by the MS 300 and is used to indicatea particular S-FA to suspend among the S-FAs actually used by the MS300. The S-FA off request may include off duration information of theS-FA 303.

Upon receiving the S-FA off request together with the SLP-REQ message,the BS 350 sends a SLP-ReSPonse (RSP) message including a response forthe S-FA off request to the MS 300 in step 315. The response for theS-FA off request includes an indicator indicative of the approval or thedisapproval of the S-FA off request of the MS 300.

The MS 300, receiving the SLP-RSP message, enters the sleep mode asindicated by the SLP-RSP message, concurrently stops using the S-FA 303,and transmits and receives data with the BS 350 over the P-FA 301 in alistening interval of the sleep mode in step 317. While the SLP-REQ/RSPprocedures are conducted in steps 313 and 315, the entrance into thesleep mode of the MS 300 may not be permitted. Even when the entranceinto the sleep mode is not permitted, the S-FA off request and/orresponse for the S-FA 303 is still effective. In this situation, the MS300 transmits and receives data with the BS 350 only through the P-FA301 without entering into the sleep mode. In contrast to FIG. 3 whenusing two or more S-FAs, the MS 300 transmit and receives data over atleast one S-FA excluding the suspended S-FA 303 and the P-FA.

The MS 300 entering into the sleep mode determines that it is possibleto transmit and receive data over the S-FA 303. Thus, to inform the BS350 of the communication resumption using the S-FA 303, the MS 300 sendsan S-FA readiness indicator over the P-FA. 301 in step 319.

The BS 350 receiving the S-FA readiness indicator determines whether toallow the use resumption of the suspended S-FA and then sends an S-FAreadiness indicator ACK to the MS 300 in step 321. Whether to allow theuse resumption of the suspended S-FA is determined based on the signalstrength measurement value of the S-FA 303 reported from the MS 300, theload of the S-FA 303, and the existence and the number of MSs using theS-FA 303 as their P-FA. The S-FA readiness indicator ACK includesinformation informing of the permission of the data transfer over theS-FA 303 of the MS 300, information informing of the prohibition on thedata transfer over the S-FA 303 of the MS 300, or information requestingto use other FA than the S-FA 303. When the use of the S-FA 303 is notpermitted, the RS 330 adds the frequency information or the FAidentifier information of the other FA to the S-FA readiness indicatorACK. At this time, it is assumed that the data delivery over the S-FA303 of the MS 300 is permitted.

After confirming the permission on the data transfer with the BS 350over the S-FA 303 from the S-FA readiness indicator ACK, the MS 300transmits and receives data with the BS 350 over the P-FA 301 in thelistening interval of the sleep mode and data with the BS 350 over theS-FA 303 in step 323. The S-FA readiness indicator and the S-FAreadiness indicator ACK used to resume the suspended S-FA in the sleepmode may be added to one of a control message of a Media Access Control(MAC) layer defined to control the sleep mode, and a MAC layer header.

The MS requests the sleep mode entrance in FIG. 3, whereas the MS mayadd the S-FA off request to the SLP-RSP message even when the BSrequests the sleep mode entrance. In this situation, the BS receivingthe SLP-RSP message including the S-FA off request from the MS,recognizes the suspension of the S-FA of the MS.

FIG. 4 is a diagram illustrating signal exchanges for S-FA on-off in anoverlay wireless communication system according to an exemplaryembodiment of the present invention. In FIG. 4, an MS 400 and a BS 450employ (N+1)-ary FAs, that is, one P-FA 401 and N-ary S-FAs 403-1through 403-N. Note that the procedures in FIG. 4 are applicable to twoFAs, that is, to one P-FA and one S-FA.

Referring to FIG. 4, the MS 400 transmits and receives data to and fromthe BS 450 over the P-FA 401 and the N-ary S-FAs 403-1 through 403-N instep 411. Herein, the P-FA 401 is determined at the initial connectionof the MS 400. Accordingly, when a plurality of MSs exists, the P-FAs ofthe MSs may be set to different FAs. That is, the P-FA of a particularMS may be the S-FA of another MS.

In the process of the data communication, the MS 400 determines tosuspend at least one of the N-ary S-FAs 403-1 through 403-N based on itsbattery status. The suspension of the at least one S-FA is determinedbased on the signal strength measurement value and the power consumptionof each S-FA. For example, when the signal strength measurement value ofthe corresponding S-FA is less than a threshold required for the datadelivery or when the remaining capacity of the battery is not enough tokeep using the (N+1)-ary S-FAs, the MS 400 determines to suspend theusage of at least one of the N-ary S-FAs 403-1 through 403-N. Hereafter,it is assumed that the S-FA1 403-1 is suspended.

Determining to suspend the S-FA1 403-1, the MS 400 sends an S-FA offrequest me sage, which requests to suspend the S-FA1 403-1, to the BS450 in step 413. The S-FA off request message includes indicationinformation of the S-FA1 403-1 requested to suspend For example, theindication information may include an index of the S-FA1 403-1 or theS-FA bitmap information representing the S-FA1 403-1. Herein, the indexis a physical carrier index or a logical carrier index. The bitmap sizeis equal to the number of the S-FAs allocated to the MS 400. When theS-FAs allocated to the MS 400 differ from the S-FAs actually used by theMS 400, the bitmap size is determined by the number of the S-FAsactually used by the MS 400 and is used to represent a particular S-FAto suspend among the S-FAs actually used by the MS 400. When the MS 400is able to predict the off duration of the S-FA1 403-1 by analyzingoccurrence of uplink data, the MS 400 adds information indicative of theoff duration to the S-FA off request message. The information indicativeof the off duration contained in the S-FA off request message may beused for the BS 450 to perform data scheduling of the MS 400.

The BS 450, receiving the off request message from the MS 400, sends anS-FA off response message in reply to the off request message in step415. Accordingly, the MS 400 and the BS 450 recognize the suspension ofthe use of the S-FA1 403-1 and transmit and receive data over the otherFAs than the suspended S-FA in step 417.

Next, when determining the resumption of the S-FA1 403-1, the MS 400sends an S-FA on request message, which requests the BS 450 to resumethe S-FA1 403-1, to the BS 450 in step 419.

Upon receiving the S-FA on request message, the BS 450 determineswhether to allow the resumption of the suspended S-FA and sends an S-FAon response message to the MS 400 in step 421. Whether to allow the useresumption of the suspended S-FA1 403-1 is determined based on thesignal strength measurement value of the S-FA1 403-1 reported from theMS 400, the load of the S-FA1 403-1, and the existence and the number ofMSs which use the S-FA1 403-1 as their P-FA. The S-FA on responsemessage includes one of the information informing of the permission onthe resumption of the suspended S-FA, the information informing of thedisapproval of the resumption of the suspended S-FA, and the informationrequesting to use other FA than the suspended S-FA. To direct to use theother FA, the BS 450 adds frequency information or FA identifierinformation of the other FA to the S-FA on response message. Hereafter,it is assumed that the communication over the suspended S-FA ispermitted.

Upon confirming the permission of the resumption of the suspended S-FAfrom the S-FA on response message, the MS 400 completes the preparationfor the resumption of the suspended S-FA and then sends an S-FAreadiness indicator in step 423. For example, the preparation for theresumption includes synchronization procedure such as ranging, hardwarestatus transition, and so on. Herein, unlike the readiness indicators ofFIGS. 2 and 3, the S-FA readiness indicator is used to inform that theresumption of the suspended S-FA may be started.

After sending the S-FA readiness indicator, the MS 400 transmits andreceives data to and from the BS 450 over the P-FA 401 and the N-aryS-FAs 403-1 through 403-N in step 425.

In FIG. 4, the MS sends the message for the off of the S-FA. Inaddition, the MS may request the suspension of the S-FA together withthe request for the sleep mode entrance, which is now described indetail by referring to FIG. 5.

FIG. 5 is a diagram illustrating signal exchanges for S-FA on-off in anoverlay wireless communication system according to an exemplaryembodiment of the present invention.

In FIG. 5, an MS 500 transmits and receives data to and from a BS 550over the P-FA 501 and the N-ary S-FAs 503-1 through 503-N in step 511.Herein, the P-FA 501 is determined at the initial connection of the MS500. Accordingly, when a plurality of MSs exists, the P-FAs of the MSsmay be set to different FAs. That is, the P-FA of a particular MS may bethe S-FA of another MS.

The MS 500 concurrently determines to enter into the sleep mode and tosuspend at least one of the N-ary S-FAs 503-1 through 503-N. Thesuspension of the S-FA is determined based on the signal strengthmeasurement value and the power consumption of each S-FA. For example,when a signal strength measurement value of the corresponding S-FA isless than a threshold required for the data delivery or when theremaining capacity of the battery is insufficient to keep using the(N+1)-ary S-FAs, the MS 500 determines to suspend the usage of at leastone of the N-ary S-FAs 503-1 through 503-N. Hereafter, it is assumedthat the S-FA1 503-1 is suspended.

The MS 500 sends a SLP-REQ message including an S-FA off request whichrequests to suspend the use of the S-FA1 503-1, to the BS 550 in step513. The S-FA off request includes indication information of the S-FA1503-1 requested to stop. For example, the indication information is oneof the frequency information of the S-FA1 503-1, the index of the S-FA1503-1, and the S-FA bitmap representing the S-FA1 503-1. Herein, theindex is the physical carrier index or the logical carrier index. Thebitmap size is equal to the number of the S-FAs allocated to the MS 500.When the S-FAs allocated to the MS 500 differ from the S-FAs actuallyused by the MS 500, the bitmap size is determined by the number of theS-FAs actually used by the MS 500 and is used to indicate a particularS-FA to suspend among the S-FAs actually used by the MS 500.

The S-FA off request may include the off duration information of thesuspended S-FA.

Upon receiving the SLP-REQ message, the BS 550 determines whether toallow the sleep mode entrance and sends a SLP-RSP message informing ofthe approval or the disapproval to the MS 500 in step 515. According tothe S-FA off request in the SLP-REQ message, the BS 550 adds an S-FA offresponse to the SLP-RSP message.

The MS 500, receiving the SLP-RSP message, enters into the sleep mode asindicated by the SLP-RSP message, concurrently stops using the S-FA1503-1, and transmits and receives data with the BS 550 over the otherFAs than S-FA1 503-1 in the listening interval of the sleep mode in step517. While the SLP-REQ/RSP procedures are conducted in step 513 and 515,the entrance into the sleep mode of the MS 500 may not be permitted.Even when the entrance into the sleep mode is not permitted, the S-FAoff request and/or response for the S-FA1 503-1 is still effective. Inthis situation, the MS 500 transmits and receives data with the BS 550over at least one FA excluding the S-FA1 503-1 without entering thesleep mode.

Next, upon determining to resume the S-FA1 503-1, the MS 500 sends anS-FA on request message, which requests the BS 550 to resume using theS-FA1 503-1, to the BS 550 in step 519. In so doing, the MS 500 mayperform the ranging procedure for the S-FA1 503-1.

Upon receiving the S-FA on request message, the BS 550 determineswhether to allow the resumption of the suspended S-FA and sends an S-FAon response message to the MS 500 in step 521. Whether to allow theusage resumption of the suspended S-FA is determined based on the loadof the suspended S-FA, and the existence and the number of MS which usethe suspended S-FA as their P-FA. The S-FA on response message includesone of the information informing of the permission on the resumption ofthe suspended S-FA of the MS 500, the information informing of thedisapproval of the resumption of the suspended S-FA of the MS 500, andthe information requesting to use other FA than the suspended S-FA. Todirect to use the other FA, the BS 550 adds frequency information or FAidentifier information of the other FA to the S-FA on response message.Hereafter, it is assumed that the usage resumption of the S-FA1 503-1 ispermitted. An S-FA readiness indicator and an S-FA readiness indicatorACK used to resume the suspended S-FA in the sleep mode may be added toone of the control message of the MAC layer defined to control the sleepmode, and the MAC layer header.

The MS 500, confirming the permission of the resumption of the suspendedS-FA from the S-FA on response message, completes the preparation forthe resumption of the suspended S-FA and then sends the S-FA readinessindicator in step 523. For example, the preparation for the resumptionincludes synchronization procedure such as ranging, hardware statustransition, and so on. Herein, unlike the readiness indicators of FIGS.2 and 3, the S-FA readiness indicator is used to inform that theresumption of the suspended S-FA may be started.

After sending the S-FA readiness indicator, the MS 500 transmits andreceives data to and from the BS 550 over the P-FA 501 and the N-aryS-FAs 503-1 through 503-N in step 525.

FIG. 6 is a diagram illustrating signal exchanges for S-FA on-off in anoverlay wireless communication system according to an exemplaryembodiment of the present invention. In FIG. 6, the broadband wirelesscommunication system includes an MS 600 and a BS 650. The MS 600 and theBS 650 employ (N+1)-ary FAs, that is, one P-FA 601 and N-ary S-FA 603-1through 603-N. Note that the procedures in FIG. 6 are applicable to twoFAs, that is, to one P-FA and one S-FA.

Referring to FIG. 6, the MS 600 transmits and receives data to and fromthe BS 650 over the P-FA 601 and the N-ary S-FAs 603-1 through 603-N instep 611. Herein, the P-FA 601 is determined at the initial connectionof the MS 600. Accordingly, when a plurality of MSs exists, the P-FAs ofthe MSs may be set to different FAs. That is, the P-FA of a particularMS may be the S-FA of another MS.

During the data communication, the BS 650 determines to suspend at leastone of the N-ary S-FAs 603-1 through 603-N in step 613. The suspensionof the S-FA is determined based on a signal strength measurement valueof each S-FA reported from the MS 600, and the load of each S-FA. Forexample, when the signal strength measurement value of the correspondingS-FA is less than a threshold required for the data delivery or when theload needs to be distributed because of the excessive load in thecorresponding S-FA, the BS 650 determines to suspend the usage of atleast one of the N-ary S-FAs 603-1 through 603-N. Hereafter, it isassumed that the S-FA1 603-1 is suspended.

The BS 650 sends an S-FA off request message for the at least one of theN-ary S-FAs 603-1 through 603-N to the MS 600 in step 615. The S-FA offrequest message includes indication information of the S-FA1 603-1requested to suspend. For example, the indication information is one ofthe frequency information of the S-FA1 603-1, the index of the S-FA1603-1, and the S-FA bitmap information representing the S-FA1 603-1.Herein, the index is the physical carrier index or the logical carrierindex. The bitmap size is equal to the n umber of the S-FAs allocated tothe MS 600. When the S-FAs allocated to the MS 600 differ from the S-FAsactually used by the MS 600, the bitmap size is determined by the number of the S-FAs actually used by the MS 600 and is used to representa particular S-FA to suspend among the S-FAs actually used by the MS600. When able to predict the off duration of the suspended S-FA byanalyzing the occurrence of downlink data, the BS 650 adds informationindicative of the off duration of the suspended S-FA to the S-FA offrequest message. In addition, the S-FA off request message may includeinformation requesting to use other FA, than the suspended S-FA. Todirect to use the other FAs, the BS 650 adds the indication informationof the other FA, for example, one of the frequency information, theindex, and the bitmap to the S-FA off request message. Herein, the indexis the physical carrier index or the logical carrier index. Hereafter,it is assumed that the information requesting to use the other FA is notincluded.

The MS 600, receiving the S-FA off request message from the BS 650,sends an S-FA off response message in reply to the S-FA off requestmessage in step 617. Accordingly, the MS 600 and the BS 650 suspend atleast one of the N-ary S-FAs 603-1 through 603-N and transmit andreceive data over the other FAs excluding the suspended S-FA in step619.

If it is determined that the resumption of the usage of the S-FA1 603-1is necessary and that the usage resumption is feasible, the BS 650 sendsan S-FA on request message requesting to resume the suspended S-FA tothe MS 600 in step 621. Whether to resume the S-FA is determined basedon criteria similar to the aforementioned S-FA suspension. Whether toresume the S-FA is determined based on the signal strength measurementvalue of each S-FA reported from the MS 600, and the load of each S-FA.For example, when a signal strength measurement value of thecorresponding S-FA is greater than a threshold required for the datadelivery or when the load in the corresponding S-FA is quite little andadditional traffic may be accommodated, the BS 650 determines that it ispossible to resume the S-FA1 603-1.

Upon receiving the S-FA on request message, the MS 600 sends an S-FA onresponse message to the BS 650 in reply to the S-FA on request messagein step 623. Next, the MS 600 completes the preparation for the usageresumption of the suspended S-FA and then sends an S-FA readinessindicator in step 625. For example, the preparation for the u ageresumption includes the synchronization procedure such a ranging, andthe hardware status transition. Herein, unlike the readiness indicatorof FIGS. 2 and 3, the S-FA readiness indicator is used to inform thatthe usage resumption of the suspended S-FA may begin.

After sending the S-FA readiness indicator, the MS 600 and the BS 650transmit and receive data over the P-FA 601 and the N-ary S-FAs 603-1through 603-N in step 627.

In FIG. 6, the MS 600 transmits the S-FA on response message and S-FAreadiness indicator upon receiving the S-FA on request message. However,according to another exemplary embodiment of the present invention, step625 where the MS 600 transmits the S-FA readiness indicator may isexcluded, and step 623 where the MS 600 transmits the S-FA on responsemessage is performed after completing the preparation for the usageresumption of the suspended S-FA. That is, the S-FA on response messageis used to reply to the S-FA on request message and to inform that theusage resumption of the suspended S-FA may begin.

In FIG. 6, the BS sends the message for turning off the S-FA. Besides,the BS may request the suspension of the S-FA together with the requestfor the sleep mode entrance, which is now explained in detail byreferring to FIG. 7.

FIG. 7 is a diagram illustrating signal exchanges for S-FA on-off in anoverlay wireless communication system according to an exemplaryembodiment of the present invention.

In FIG. 7, an MS 700 transmits and receives data to and from a BS 750over the P-FA 701 and the N-ary S-FAs 703-1 through 703-N in step 711.Herein, the P-FA 701 is determined at the initial connection of the MS700. Accordingly, when a plurality of MSs exists, the P-FAs of the MSsmay be set to different FAs. That is, the P-FA of a particular MS may bethe S-FA of another MS.

In the process of the data communication, the MS 700 determines to enterinto the sleep mode and sends an SLP-REQ message to the BS 750 in step713. The BS 750 determines to suspend at least one of the N-ary S-FAs703-1 through 703-N in step 715. The usage suspension of the S-FA isdetermined based on the load of each S-FA, the signal strengthmeasurement value of each S-FA reported from the MS 700, and so forth.For example, when a signal strength measurement value of thecorresponding S-FA is less than a threshold required for the datadelivery or when the load needs to be distributed because of theexcessive load in the corresponding S-FA, the BS 750 determines tosuspend the usage of at least one of the N-ary S-FAs 703-1 through703-N. Hereafter, it is assumed that the S-FA1 703-1 is suspended.

Upon receiving the SLP-REQ message, the BS 750 determines whether toallow the sleep mode entrance of the MS 700 and sends an SLP-RSP messageinforming of the approval or the disapproval in step 717. The SLP-RSPmessage includes the S-FA off request which requests to suspend theS-FA1 703-1 as determined in step 715. The S-FA off request includesindication information of the S-FA1 703-1 requested to be suspended. Forexample, the indication information is one of the frequency informationof the S-FA1 703-1, an index of the S-FA1 703-1, and the S-FA bitmaprepresenting the S-FA1 703-1. Herein, the index is the physical carrierindex or the logical carrier index. The bitmap size is equal to thenumber of the S-FAs allocated to the MS 700. When the S-FAs allocated tothe MS 700 differ from the S-FAs actually used by the MS 700, the bitmapsize is determined by the number of the S-FAs actually used by the MS700 and is used to indicate a particular S-FA to suspend among the S-FAsactually used by the MS 700. The S-FA off request may include the offduration information of the S-FA1 703-1.

Upon receiving the S-FA off request contained in the SLP-RSP message,the MS 700 recognizes that it is necessary to suspend the S-FA1 703-1and sends an S-FA off response message including a response for the S-FAoff request to the BS 750 in step 719. Next, the MS 700 receiving theSLP-RSP message enters into the sleep mode as indicated by the SLP-RSPmessage, simultaneously suspends the S-FA1 703-1, and transmits andreceives data with the BS 750 over the FAs excluding the S-FA1 703-1 inthe listening interval of the sleep mode in step 721. While the sleeprequest and/or response procedures are performed in steps 713 and 717,the sleep mode entrance of the MS 700 may not be permitted. Even whenthe sleep mode entrance is not permitted, the S-FA off request and/orresponse for the S-FA1 703-1 is still valid. In this situation, the MS700 transmits and receives data to and from the BS 750 over the otherFAs excluding the S-FA1 703-1 without entering to the sleep mode.

Next, when determining that the resumption of the usage of the S-FA1703-1 is necessary and that the usage resumption is feasible, the BS 750sends an S-FA on request message requesting to resume the S-FA1 703-1 tothe MS 600 in step 723. Whether to resume the S-FA is determined basedon criteria similar to the aforementioned S-FA suspension. Whether toresume the S-FA is determined based on the signal strength measurementvalue of each S-FA reported from the MS 700, and the load of each S-FA.For example, when the signal strength measurement value of thecorresponding S-FA is greater than a threshold required for the datadelivery or when the load in the corresponding S-FA is quite little andadditional traffic may be accommodated, the BS 750 determines that it ispossible to resume the S-FA1 703-1.

Upon receiving the S-FA on request message, the MS 700 sends an S-FA onresponse message to the BS 750 in reply to the S-FA on request messagein step 725. Next, the MS 700 completes the preparation for the usageresumption of the suspended S-FA and then sends an S-FA readinessindicator in step 727. For example, preparation for resumption includesthe synchronization procedure such as ranging, and the hardware statustransition. Herein, unlike the readiness indicators of FIGS. 2 and 3,the S-FA readiness indicator is used to inform that the usage resumptionof the suspended S-FA may begin. The S-FA readiness indicator and anS-FA readiness indicator ACK used to resume the suspended S-FA in thesleep mode may be added to one of the control message of the MAC layerdefined to control the sleep mode, and the layer header.

After sending the S-FA readiness indicator, the MS 700 an BS 750transmit and receive data over the P-FA 701 and the N-ary S-FAs 703-1through 703-N in step 729.

In FIG. 7, the MS 700 transmits the S-FA on response message and S-FAreadiness indicator upon receiving the S-FA on request message. However,according to another exemplary embodiment of the present invention, step727 where the MS 700 transmits the S-FA readiness indicator may isexcluded, and step 725 where the MS 700 transmits the S-FA on responsemessage is performed after completing the preparation for the usageresumption of the suspended S-FA. That is, the S-FA on response messageis used to reply to the S-FA on request message and to inform that theusage resumption of the suspended S-FA may begin.

In FIGS. 2 through 7, it is assumed that the off state of the S-FA doesnot affect Quality of Service (QoS) policy for the MS. In a case wherethe S-FA off operation of the MS affects the QoS policy, the MS and theBS need to additionally perform a dynamic service negotiation procedure,for example, a Dynamic Service Change (DSC) procedure. In other words,even when the state of the S-FA decreases the available radio resources,the MS and the BS have to modify QoS parameters of the ongoing serviceflow so as to the required QoS according to the QoS policy.

In this case, the procedures of transmitting and receiving the S-FA onrequest message and the S-FA on response message in FIGS. 4 through 7may be included to the dynamic service negotiation procedure. That is,by including the contents of the S-FA on request message and the S-FA orresponse message to the message transmitted and received for the dynamicservice negotiation procedure, the MS and the BS may process the dynamicservice negotiation procedure and the S-FA usage resumption procedure asa single procedure.

Now, structures and operations of the MS and the BS for turning on/offthe S-FA as stated above are elucidated by referring to the drawings.

FIG. 8 is a flowchart illustrating operations of an MS in a broadbandwireless communication system according to an exemplary embodiment ofthe present invention.

In step 801, the MS communicates over the P-FA and at least one S-FA,That is, the MS transmits and receives data to and from the BS using allof the multiple FAs.

In step 803, the MS determines whether it is necessary to reduce thepower consumption by stopping using the S-FA. More specifically, the MScontinuously monitors its battery status and determines based on thebattery status whether to reduce the power consumption. For instance, ifit is determined that the remaining capacity of the battery falls belowthe threshold, the MS determines to reduce the power consumption. To thecontrary, when the signal strength measurement value for the S-FA isless than threshold required for the data delivery, the MS may determinethat the suspension of the corresponding S-FA is required. When thesuspension of the S-FA is unnecessary, the MS returns back to step 801.

When the suspension of the S-FA is required, the MS sends an S-FA offrequest message to the BS in step 805. The S-FA off request messageincludes the indication information of the S-FA requested to suspend.For example, the indication information is one of the frequencyinformation of the S-FA, the index of the S-FA, and the S-FA bitmaprepresenting the S-FA. Herein, the index is the physical carrier indexor the logical carrier index. When able to predict the off duration ofthe S-FA by analyzing the occurrence of the uplink data, the MS sendsthe S-FA off request message including the off duration information.

In step 807, the MS determines whether the S-FA off response message isreceived from the BS. Herein, the S-FA off response message includes theindicator indicative of the approval or the disapproval on the usagesuspension request of the S-FA.

In step 809, the MS communicates only over the P-FA. When using two ormore S-FAs, the MS communicates over the other S-FAs than the suspendedS-FA and the P-FA. In more detail, the MS confirms the approval of itsS-FA suspension request from the S-FA off response message, andrecognizes that no data is received over the suspended S-FA. Thus, theMS does not operate to maintain the synchronization for the suspendedS-FA and to receive the control message in the suspended S-FA.

In step 811, the MS determines whether the use of the suspended S-FA maybe resumed. Namely, the MS determines whether the usage of the suspendedS-FA is resumed, based on the battery status or the signal strengthmeasurement value. The MS determines whether the remaining batterycapacity is enough to accommodate the power consumption increased by theresumption of the suspended S-FA, or whether the signal strengthmeasurement value of the suspended S-FA is greater than the threshold.When the suspended S-FA may not be resumed, the MS returns to step 809.

When the suspended S-FA is resumed, the MS sends an S-FA readinessindicator to the BS in step 813. Although it is not illustrated in FIG.8, before sending the S-FA readiness indicator, the MS may perform theranging procedure on the S-FA if necessary. For instance, when the S-FAis physically close to the P-FA, frequency/time adjustment value of theP-FA may be applied to the S-FA. By contrast, when the S-FA is notphysically close to the P-FA, it is not preferable to apply thefrequency/time adjustment value of the P-FA to the S-FA. Hence, the MSconducts the ranging procedure on the S-FA.

In step 815, the MS determines whether an S-FA readiness indicator ACKis received from the BS. The S-FA readiness indicator ACK informs of thedetermination result of the BS with respect to the S-FA usage resumptionrequest of the MS. Herein, the determination result of the BS is one ofthe usage approval of the S-FA, the usage disapproval of the S-FA, andthe instruction to use other FA.

When receiving the S-FA readiness indicator ACK, the MS confirms thedetermination result of the BS from the S-FA readiness indicator ACK instep 817. More specifically, the MS determines whether the usage of theS-FA is approved, the usage of the S-FA is disapproved, or the usage ofanother FA is instructed. When the usage of the S-FA is allowed, the MSreturns back to step 801. When the usage of the S-FA is not allowed, theMS returns back to step 809.

When the usage of the other FA is instructed, the MS sets the other FAas its S-FA in step 819. That is, the MS determines to use the other FAas its S-FA as instructed by the BS. To set the other FA as the S-FA,the MS may perform the ranging on the other FA. Next, the MS returns tostep 801.

Another exemplary implementation of the MS is now illustrated.

In step 805, the MS requests to enter into the sleep mode and to suspendthe S-FA at the same time. In other words, the MS sends the SLP-REQmessage including the S-FA off request. In step 807, the MS determineswhether the SLP-RSP message including the S-FA off response is received.Next, the MS confirms whether the sleep mode entrance is approved, fromthe SLP-RSP message. Since the sleep mode entrance may not be permittedwhile the suspension request of the S-FA is accepted, the MS examineswhether the sleep mode entrance is approved. When the sleep modeentrance is approved, the MS enters the sleep mode and communicates overat least one FA excluding the suspended S-FA in step 809. When the sleepmode entrance is not permitted, the MS communicates in at least one FAexcluding the suspended FA without entering the sleep mode in step 809.

Yet another exemplary implementation of the MS is now described.

In step 813, the MS sends an S-FA on request message to the BS. In step815, the MS determines whether an S-FA on response message is received.Herein, the S-FA on response message includes one of the informationinforming of the approval of the usage resumption of the suspended S-FA,the information informing of the disapproval of the usage resumption ofthe suspended S-FA, and the information requesting to use other FA thanthe suspended S-FA. When the information informing of the disapproval ofthe usage resumption of the suspended S-FA is included, the MS returnsback to step 809. When the information requesting to use other FA isincluded, the MS proceeds to step 819. When the information informing ofthe approval of the usage resumption of the suspended S-FA is carried,the MS completes the preparation for the resumption of the suspendedS-FA and sends the S-FA readiness indicator. For example, thepreparation for the usage resumption includes the synchronizationprocedure such as ranging, and the hardware status transition.

Still another exemplary implementation of the MS is now described.

In step 805, the MS requests to enter into the sleep mode andsimultaneously requests to stop using the S-FA. That is, the MS sendsthe SLP-REQ message including the S-FA off request. In step 807, the MSdetermines whether the SLP-RSP message including the S-FA off responseis received. Next, based on the SLP-RSP message, the MS confirms theapproval or the disapproval of the sleep mode entrance. Since the sleepmode entrance may not be approved while the S-FA suspension request isaccepted, the MS confirms the approval or the disapproval of the sleepmode entrance. When the sleep mode entrance is allowed, the MS entersthe sleep mode and communicates over at least one FA excluding thesuspended S-FA in the listening interval in step 809. By contrast, whenthe sleep mode entrance is not allowed, the MS communicates over atleast one FA excluding the suspended S-FA in the listening intervalwithout entering into the sleep mode in step 809.

In step 813, the MS sends an S-FA on request message to the BS. In step815, the MS determines whether an S-FA on response message is received.Herein, the S-FA on response message includes one of the informationinforming of the approval of the usage resumption of the suspended S-FA,the information informing of the disapproval of the usage resumption ofthe suspended S-FA, and the information requesting to use other FA thanthe suspended S-FA. When the information informing of the disapproval ofthe usage resumption of the suspended S-FA is included, the MS returnsback to step 809. When the information requesting to use other FA isincluded, the MS proceeds to step 819. When the information informing ofthe approval of the usage resumption of the suspended S-FA is carried,the MS completes the preparation for the resumption of the suspendedS-FA and sends the S-FA readiness indicator. For example, thepreparation for the usage resumption includes the synchronizationprocedure such as ranging, and the hardware status transition.

FIG. 9 is a flowchart illustrating operations of a BS in a broadbandwireless communication system according to an exemplary embodiment ofthe present invention.

In step 901, the BS determines whether an S-FA off request message isreceived from the MS. More specifically, the BS determines whether theusage suspension of the S-FA is requested from the MS which iscommunicating over the P-FA and the S-FA. The S-FA off request messageis received over the P-FA of the MS. The S-FA off request messageincludes the indication information of the S-FA requested to suspend.For example, the indication information is one of the frequencyinformation of the S-FA, the index of the S-FA, and the S-FA bitmaprepresenting the S-FA. Herein, the index is the physical carrier indexor the logical carrier index.

Receiving the S-FA off request message, the BS updates FA use statusinformation of the MS in step 903. By receiving the S-FA off requestmessage, the BS determines to suspend the usage of the S-FA at the MS.Correspondingly, to reflect the suspension of the S-FA in the resourceallocation, the BS excludes the S-FA from a list of the used FAs of theMS. Consequently, the resource in the S-FA is not allocated to the MS.When the S-FA off request message includes the off duration information,the BS reflects the off duration information to its scheduling.

In step 905, the BS sends an S-FA off response message to the MS.Herein, the S-FA off response message includes the indicator indicativeof the approval or the disapproval of the suspension request of theS-FA.

In step 907, the BS determines whether an S-FA readiness indicator isreceived from the MS. That is, the BS determines whether the MS requeststhe resumption of the S-FA.

Upon receiving the S-FA readiness indicator, the BS determines whetherthe usage of the S-FA may be allowed in step 909. Herein, whether topermit the use of the S-FA is determined based on the load of the S-FA,the existence and the number of the MSs which employ the S-FA as theirP-FA.

When the use of the S-FA may be allowed, the BS sends an S-FA readinessindicator ACK notifying of the approval of the S-FA usage to the MS instep 911. Next, the BS updates the FA use status information of the MS.

In contrast, when not allowing the use of the S-FA in step 909, the BSdetermines whether to permit the usage of other FA in step 913. The BSexamines whether there exists the FA usable by the MS among the FAsexcept for the S-FA and the P-FA of the MS. Herein, whether to allowusing the other FA is determined based on a resource usage rate of theother FA, and the existence and the number of the MSs which employ theother FA as the P-FA.

When the usage of the other FA is allowable in step 913, the BS sendsthe S-FA readiness indicator ACK instructing to use the other FA, to theMS in step 915. Next, the BS updates the FA use status information ofthe MS.

In contrast, when the usage of the other FA is not allowable in step913, the BS sends the S-FA readiness indicator ACK notifying of thedisapproval of the S-FA use in step 917.

Another exemplary implementation of the BS is now described.

The BS determines whether the SLP-REQ message is received from the MS.Upon receiving the SLP-REQ message, the BS determines whether theSLP-REQ message includes the S-FA off request in step 901. When theSLP-REQ message includes the S-FA off request, the BS proceeds to step903. Next, the BS determines whether to allow the sleep mode entrance ofthe MS. In step 905, the BS sends the SLP-RSP message notifying of theapproval or the disapproval of the sleep mode entrance. The SLP-RSPmessage includes the S-FA off response.

Yet another exemplary implementation of the BS is now described.

In step 907, the BS determines whether the S-FA on request message isreceived. Herein, the S-FA on request message informs of the request ofthe resumption of the suspended S-FA. Upon receiving the S-FA on requestmessage, the BS proceeds to step 909. In step 911, 915 or 917, the BSsends an S-FA on response message including one of the informationinforming of the approval of the usage resumption of the suspended S-FA,the information informing of the disapproval of the usage resumption ofthe suspended S-FA, and the information requesting to use other FA thanthe suspended S-FA. Next, the BS determines whether the S-FA readinessindicator is received from the MS. Receiving the S-FA readinessindicator, the BS updates the FA use status information of the MS.

Still another exemplary implementation of the BS is now described.

The BS determines whether the SLP-REQ message is received from the MS.Upon receiving the SLP-REQ message, the BS determines whether theSLP-REQ message includes the S-FA off request in step 901. When theSLP-REQ message includes the S-FA off request, the BS proceeds to step903. Next, the BS determines whether to allow the sleep mode entrance ofthe MS. In step 905, the BS sends the SLP-RSP message informing of theapproval or the disapproval of the sleep mode entrance. The SLP-RSPmessage includes the S-FA off response.

In step 907, the BS determines whether the S-FA on request message isreceived. Herein, the S-FA on request message informs of the request toresume the suspended S-FA. When receiving the S-FA on request message,the BS proceeds to step 909. In step 911, 915 or 917, the BS sends anS-FA on response message including one of the information informing ofthe approval of the usage resumption of the suspended S-FA, theinformation informing of the disapproval of the usage resumption of thesuspended. S-FA, and the information requesting to use other FA than thesuspended S-FA. Next, the BS determines whether the S-FA readinessindicator is received from the MS. Receiving the S-FA readinessindicator, the BS updates the FA use status information of the MS.

FIG. 10 is a flowchart illustrating operations of a BS in a broadbandwireless communication system according to an exemplary embodiment ofthe present invention.

In step 1001, the BS communicates with the MS over the P-FA and at leastone S-FA. That is, the BS transmits and receives data to and from the MSusing all of the multiple FAs.

In step 1003, the BS determines whether to need to suspend the use of atleast one S-FA. The suspension of the at least one S-FA is determinedbased on a signal strength measurement value of each S-FA reported fromthe MS, and the load of each S-FA. For example, when the signal strengthmeasurement value of the corresponding S-FA is less than a thresholdrequired for the data delivery or when the load needs to be distributedbecause of the excessive load in the corresponding S-FA, the BSdetermines to suspend the usage of at least one S-FA. In so doing, thesubject of the suspension is all or part of the at least one S-FA.

When determining to suspend the use of the at least one S-FA, the BSdetermines whether it possible to allow using other FA in step 1005. Inother words, the BS determines whether a new FA may be allocated inplace of the suspended S-FA.

When the use of the other FA is not allowable, the BS sends the S-FArequest message including the indication information of the suspendedS-FA in step 1007. By contrast, when the use of the other FA isallowable, the BS sends the S-FA request message including theindication information of the suspended S-FA and the newly allowed FA instep 1009. For example, the indication information is one of thefrequency information of the corresponding FA, the index, and the S-FAbitmap representing the corresponding FA. Herein, the index is thephysical carrier index or logical carrier index. When the BS is able topredict the off duration of the suspended S-FA by analyzing theoccurrence of the downlink data, the BS adds the information indicativeof the off duration to the S-FA off request message.

In step 1011, the BS determines whether an S-FA off response message isreceived from the MS. The BS determines whether the MS receives the usesuspension instruction of the S-FA.

Receiving the S-FA off response message, the BS communicates over one ormore FAs including the P-FA in step 1013. Namely, the BS communicatesover the at least one FA for the suspended S-FA.

In step 1015, the BS determines whether the usage resumption of thesuspended S-FA is determined. The BS determines whether the usageresumption of the suspended S-FA is necessary and whether the usageresumption is feasible. Whether the usage resumption of the S-FA isfeasible is determined based on the criteria similar to theaforementioned S-FA usage suspension. Whether it is possible to resumethe S-FA is determined based on the signal strength measurement value ofeach S-FA reported from the MS, and the load of each S-FA. For example,when the signal strength measurement value of the corresponding S-FA isgreater than the threshold required for the data delivery or when theload in the corresponding S-FA is quite little and additional trafficmay be accommodated, the BS determines that it is possible to resume theS-FA.

Upon determining to resume the suspended S-FA, the BS sends an S-FA onrequest message including the indication information of the resumed S-FAin step 1017. For example, the indication information is one of thefrequency information of the corresponding FA, the index, and the S-FAbitmap representing the corresponding FA. Herein, the index is thephysical carrier index or the logical carrier index.

In step 1019, the BS determines whether the S-FA on response message andan S-FA readiness indicator are received from the MS in sequence.Herein, the S-FA on response message notifies of the reception of theS-FA on request and the S-FA readiness indicator notifies of thereadiness for the resumption of the S-FA. Hence, the BS confirms fromthe S-FA on response message that the MS received the S-FA on request,confirms the readiness for the resumption of the S-FA based on the S-FAreadiness indicator, and then returns back to step 1001.

Another exemplary implementation of the BS is now described.

In the communication over the P-FA and the at least one S-FA in step1001, upon receiving the SLP-REQ message from the MS, the BS determineswhether to permit the sleep mode entrance of the MS. In step 1003, theBS determines whether it is necessary to suspend the usage of the atleast one S-FA. Upon determining to suspend the at least one S-FA, theBS sends the SLP-RSP message informing of the approval or thedisapproval of the sleep mode entrance in step 1007 or step 1009. Atthis time, the SLP-RSP message includes the S-FA off request. The S-FAoff request includes the indication information of at least one of thesuspended S-FA and the permitted FA. For example, the indicationinformation is one of the frequency information of the corresponding FA,the index, and the S-FA bitmap representing the corresponding FA. Theindex is the physical carrier index or the logical carrier index. Whenable to predict the off duration of the suspended S-FA by analyzing theoccurrence of downlink data, the BS adds the information indicative ofthe off duration to the S-FA off request message. Next, the BS proceedsto step 1011.

Referring FIG. 10, the BS returns to step 1001 from step 1019 when theS-FA on response message and an S-FA readiness indicator are receivedfrom the MS. However, according to another exemplary embodiment of thepresent invention, the S-FA readiness indicator is not considered. Inthis case, in step 1019, if the S-FA on response message is receivedfrom the MS, then the BS returns to step 1001. That is, the S-FA onresponse message is used to reply to the S-FA on request message and toinform that the usage resumption of the suspended S-FA may begin.

FIG. 11 is a flowchart illustrating operations of an MS in a broadbandwireless communication system according to an exemplary embodiment ofthe present invention.

In step 1101, the MS communicates with the BS over the P-FA and at leastone S-FA. Namely, the MS transmits and receives data to and from the BSusing all of the multiple FAs.

In step 1103, the MS determines whether the S-FA off request message isreceived from the BS. The S-FA off request message directs to suspendthe use of all or part of the at least one S-FA, and includes indicationinformation of at least one of the suspended S-FA and the newly allowedFA. For example, the indication information is one of the frequencyinformation of the corresponding FA, the index, and the S-FA bitmaprepresenting the corresponding FA. Herein, the index is the physicalcarrier index or the logical carrier index. In addition, the S-FA offrequest may carry the information indicative of the off duration of thesuspended S-FA.

Upon receiving the S-FA off request message, the MS stops using the S-FAindicated by the S-FA off request message in step 1105. That is, the MSdoes not maintain the synchronization for the suspended S-FA and receivethe control message over the suspended S-FA.

In step 1107, the MS determines whether the S-FA off request messageincludes the use instruction of the other FA. The MS determines whetherthe S-FA off request message includes the indication information of thenewly allowed FA. When the use instruction of the other FA is notcontained, the MS proceeds to step 1111.

When the use instruction of the other FA is contained, the MS sets theother FA as its S-FA in step 1109. That is, the MS determines to utilizethe other FA as the S-FA as instructed by the BS. To set the other FA tothe S-FA, the MS may perform the ranging on the other FA.

In step 1111, the MS sends an S-FA off response message to the BS.Accordingly, the BS may acquire that the MS received the S-FA offrequest.

In step 1113, the MS communicates over one or more FAs including theP-FA. The MS communicates over at least one FA excluding the suspendedS-FA.

In step 1115, the MS determines whether the S-FA on request message isreceived from the BS. The S-FA on request message requests to resume theuse of the suspended S-FA and includes the indication information of thesuspended S-FA. For example, the indication information is the frequencyinformation of the corresponding FA, the index, and the S-FA bitmaprepresenting the corresponding FA. Herein, the index is the physicalcarrier index or the logical carrier index.

Receiving the S-FA on request message, the MS sends an S-FA on responsemessage to the BS in step 1117. Thus, the BS acquires that the MSreceived the S-FA on request.

In contrast, if it is determined that the S-FA on request message is notreceived from the BS in step 1115, the MS returns to step 1113.

In step 1119, the MS prepares for the usage resumption of the suspendedS-FA. For example, the preparation for the usage resumption includes thesynchronization procedure such as ranging, and the hardware statustransition.

In step 1121, the MS sends the S-FA readiness indicator. Herein, an S-FAreadiness indicator notifies that the use resumption of the suspendedS-FA may be commenced. After sending the S-FA readiness indicator, theMS returns to step 1101.

Another exemplary implementation of the MS is now described.

While communicating over the P-FA and one or more S-FAs in step 1101,the MS determines to enter into the sleep mode and sends the SLP-REQmessage to the BS. Next, upon receiving the SLP-RSP message from the BS,the MS determines whether the sleep mode entrance is permitted. In step1103, the MS determines whether the SLP-RSP message includes the S-FAoff request. The S-FA off request directs to stop using all or part ofthe one or more S-FAs and includes the indication information of atleast one of the suspended S-FA and the newly allowed FA. For example,the indication information is one of the frequency information of thecorresponding FA, the index, and the S-FA bitmap representing thecorresponding S-FA. Herein, the index is the physical carrier index orthe logical carrier index. In addition, the S-FA off request may includethe information indicative of the off duration of the suspended S-FA.

Referring FIG. 11, the MS transmits the S-FA on response message in step1117, prepares to resume the suspended S-FA in step 1119 and transmitsthe S-FA readiness indicator. However, according to another exemplaryembodiment of the present invention, the step 1121 where the MStransmits the S-FA readiness indicator may is excluded, and step 1117where the MS 700 transmits the S-FA on response message is performedafter step 1119 where completing the preparation for the usageresumption of the suspended S-FA. That is, the S-FA on response messageis used to reply to the S-FA on request message and to inform that theusage resumption of the suspended S-FA may begin.

Referring FIG. 11, the MS transmits the S-FA off response message instep 1111 after stopping the use of the S-FA or setting the other FA asits S-FA. However, according to another exemplary embodiment of thepresent invention, the step 1111 where the MS transmits the S-FA offresponse message is performed before step 1105 where the MS stops usingthe S-FA. That is, upon receiving the S-FA off request message, the MStransmit the S-FA off response message before stopping the use of theS-FA.

FIG. 12 is a block diagram illustrating an MS in a wirelesscommunication system according to an exemplary embodiment of the presentinvention.

The MS of FIG. 12 includes a plurality of encoders 1202-1 through1202-N, a plurality of symbol modulators 1204-1 through 1204-N, asubcarrier mapper 1206, an OFDM modulator 1208, a Radio Frequency (RF)transmitter 1210, an RF receiver 1212, an OFDM demodulator 1214, asubcarrier demapper 1216, a plurality of symbol demodulators 1218-1through 1218-N, a plurality of decoders 1220-1 through 1220-N, a databuffer 1222, a message generator 1224, a message analyzer 1226, a powerconsumption regulator 1228, and a communication controller 1230.

The encoders 1202-1 through 1202-N each encode a data bit streamtransmitted over the respective FAs. The symbol modulators 1204-1through 1204-N modulate the encoded bit stream to transmit over therespective FAs and convert to complex symbols. The subcarrier mapper1206 maps the complex symbols output from the symbol modulators 1204-1through 1204-N into the frequency domain. Since the symbol modulators1204-1 through 1204-N correspond to the FAs respectively, the subcarriermapper 1206 maps the complex symbols output from the symbol modulators1204-1 through 1204-N to the frequency region of the multiple FAs. TheOFDM modulator 1208 converts the complex symbols mapped to the frequencydomain to time-domain signals using an Inverse Fast Fourier Transform(IFFT) operation, and constitutes OFDM symbols by inserting a CyclicPrefix (CP). The RF transmitter 1210 up-converts the OFDM symbols to anRE signal and transmits the RF signal via an antenna.

The RF receiver 1212 down-converts RF signal received via the antenna toa baseband signal. The OFDM demodulator 1214 divides the baseband signaloutput from the RF receiver 1212 on the OFDM symbol basis, eliminatesthe CP, and restores the frequency-domain complex symbols using a FastFourier Transform (FFT) operation. The subcarrier demapper 1216 extractsthe complex symbols mapped to the allocated resource from thefrequency-domain complex symbols. The subcarrier demapper 1216 dividesthe complex, symbols on the FA basis and distributes the complex symbolsto the symbol demodulators 1218-1 through 1218-N. The symboldemodulators 1218-1 through 1218-N each demodulate and convert thecomplex symbols to the encoded bit stream. The decoders 1220-1 through1220-N each decode the encoded bit stream. The data buffer 1222temporarily stores the data exchanged with the BS and outputs the storeddata under the control of the communication controller 1230.

The message generator 1224 generates a control message to send to theBS. For example, the message generator 1224 generates at least one ofthe S-FA off request message to request to stop using the S-FA, theSLP-REQ message including the S-FA off request, an S-FA readinessindicator to request to use the suspended S-FA, the S-FA on requestmessage to request to use the suspended S-FA, the S-FA readinessindicator informing that the usage resumption of the suspended S-FA maystart, the S-FA off response message notifying of the reception of theS-FA off request, and the S-FA on response message notifying of thereception of the S-FA on request. When generating one of the S-FA offrequest message, the SLP-REQ message including the S-FA off request, andthe S-FA on request message, the message generator 1224 may add theindication information and the off duration information of the suspendedS-FA. For example, the indication information is one of the frequencyinformation of the corresponding FA, the index, and the S-FA bitmaprepresenting the corresponding FA. Herein, the index is either thephysical carrier index or the logical carrier index.

The message analyzer 1226 analyzes the control message received from theBS and provides the information obtained from the control message to thecommunication controller 1230. For instance, the message analyzer 1226analyzes at least one of an S-FA off response message, an SLP-RSPmessage including the S-FA off response, an S-FA readiness indicatorACK, the S-FA on response message, an S-FA off request message, the S-FAon request message, and the SLP-RSP message including the S-FA offrequest message. More particularly, as analyzing one of the S-FAreadiness indicator ACK and the S-FA on response message, the messageanalyzer 1226 attains the determination result of the BS including atleast one of the approval of the usage resumption of the suspended S-FA,the disapproval of the usage resumption of the suspended S-FA, and theallowance of the new FA usage. As analyzing one of the S-FA off requestmessage and the SLP-RSP message including the S-FA off request, themessage analyzer 1226 acquires at least one of the use suspensionrequest of the S-FA and the allowance of the other FA usage.

The power consumption regulator 1228 monitors the battery status of theMS. The power consumption regulator 1228 determines whether to reducethe power consumption based on the battery status. For instance, whenthe remaining battery capacity falls below the threshold, the powerconsumption regulator 1228 determines to reduce the power consumption.Hence, power consumption regulator 1228 determines to stop using theS-FA or to reduce the power consumption in other manners. According tothe battery status, the power consumption regulator 1228 determineswhether to resume the use of the suspended S-FA. Determining to reducethe power consumption by turning off the S-FA or determining to resumethe use of the suspended S-FA, the power consumption regulator 1228informs the communication controller 1230 of its determination.

The communication controller 1230 controls the functions for thecommunication of the MS. More particularly, the communication controller1230 controls the operations and the signalings for the suspension andthe resumption of the S-FA usage. The detailed operations of thecommunication controller 1230 are now described in the variousembodiments of the present invention.

In an exemplary implementation, when the power consumption regulator1228 notifies of the necessity of the power consumption reduction bysuspending the use of S-FA, the communication controller 1230 controlsthe message generator 1224 to generate the S-FA off request message.Meanwhile, when the signal strength measurement value of thecorresponding S-FA is less than the threshold required for the datadelivery, the communication controller 1230 itself determines thenecessity of the usage suspension of the S-FA and controls the messagegenerator 1224 to generate the S-FA off request message. The S-FA offrequest message is transmitted to the BS through the encoders 1202-1through 1202-N, the symbol modulators 1204-1 through 1204-N, thesubcarrier mapper 1206, the OFDM modulator 1208, and the RF transmitter1210. Next, when the message analyzer 1226 confirms the S-FA offresponse message, the communication controller 1230 controls tocommunicate over at least one S-FA excluding the suspended S-FA.Determining that the usage of the suspended S-FA may be resumed, thecommunication controller 1230 controls the message generator 1224 togenerate the S-FA readiness indicator. Herein, the usage resumption ofthe suspended S-FA is determined by the battery status or the signalintensity measurement value notified from the power consumptionregulator 1228. Before controlling to generate the S-FA readinessindicator, the communication controller 1230 may perform the rangingprocedure on the suspended S-FA. When the message analyzer 1226 receivesthe S-FA readiness indicator ACK and confirms the determination resultof the BS, the communication controller 1230 controls the MS to operateaccording to the determination result.

In an exemplary implementation, notably, when determining the necessityof the sleep mode entrance and the usage suspension of the S-FA, thecommunication controller 1230 controls the message generator 1224 togenerate the SLP-REQ message including the S-FA off request. When themessage analyzer 1226 confirms the SLP-RSP message including the S-FAoff response, the communication controller 1230 controls to communicatein at least one S-FA excluding the suspended S-FA, and the P-FA.

In an exemplary implementation, notably, when determining that the useof the suspended S-FA may be resumed, the communication controller 1230controls the message generator 1224 to generate the S-FA on requestmessage. Next, when the message analyzer 1226 receives the S-FA onresponse message and confirms the determination result of the BS, thecommunication controller 1230 controls the functions of the MS tooperate according to the determination result. When the usage resumptionof the suspended S-FA is allowed, the communication controller 1230completes the preparation for the use resumption of the suspended S-FA,and controls the message generator 1224 to generate the S-FA readinessindicator. By way of example, the preparation for the use resumptionincludes the synchronization procedure such as ranging, and the hardwarestatus transition.

In an exemplary implementation, distinctively, when determining thenecessity of the sleep mode entrance and the usage suspension of theS-FA, the communication controller 1230 controls the message generator1224 to generate the SLP-REQ message including the S-FA off request.When the message analyzer 1226 confirms the SLP-RSP message includingthe S-FA off response, the communication controller 1230 controls tocommunicate in at least one S-FA excluding the suspended S-FA, and theP-FA. When determining that the use of the suspended S-FA ma be resumed,the communication controller 1230 controls the message generator 1224 togenerate the S-FA on request message. Next, when the message analyzer1226 confirms the reception of the S-FA on response message and thedetermination result of the BS, the communication controller 1230controls the functions of the MS to operate according to thedetermination result. In so doing, when the use resumption of thesuspended S-FA is allowed, the communication controller 1230 completesthe preparation for the use resumption of the suspended S-FA, and thencontrols the message generator 1224 to generate the S-FA readinessindicator. For example, the preparation for the use resumption includesthe synchronization procedure such as ranging, and the hardware statustransition.

In an exemplary implementation, when the message analyzer 1226 confirmsthe S-FA off request message from the BS, the communication controller1230 stops using the S-FA indicated by the S-FA off request message.When the S-FA off request message includes the use instruction of theother FA, the communication controller 1230 sets the other FA to itsS-FA. To define the other FA as the S-FA, the communication controller1230 may perform the ranging on the other FA. Next, the communicationcontroller 1230 controls the message generator 1224 to generate the S-FAoff response message. The S-FA off response message is transmitted tothe BS through the encoders 1202-1 through 1202-N, the symbol modulators1204-1 through 1204-N, the subcarrier mapper 1206, the OFDM modulator1208; and the RF transmitter 1210. Next, the communication controller1230 controls to communicate, over at least one FA except for thesuspended S-FA. When the message analyzer 1226 confirms the S-FA onrequest message from the BS, the communication controller 1230 controlsthe message generator 1224 to generate the S-FA on response message, andprepares for the usage resumption of the suspended S-FA. For example,the preparation for the use resumption includes the synchronizationprocedure such as ranging, and the hardware status transition. Aftergetting ready to resume the suspended S-FA, the communication controller1230 controls the message generator 1224 to generate the S-FA readinessindicator. Herein, the S-FA readiness indicator notifies that theresumption of the suspended S-FA may begin.

In an exemplary implementation, distinctively, when the entrance intothe sleep mode is determined, the communication controller 1230 controlsthe message generator 1224 to generate the SLP-REQ message. When themessage analyzer 1226 confirms the SLP-RSP message, the communicationcontroller 1230 confirms the approval or the disapproval of the sleepmode entrance and determines whether the SLP-RSP message includes theS-FA off request. When the S-FA off request is contained, thecommunication controller 1230 operates the same as in the case where theS-FA off request message is received in the further exemplary embodimentof the present invention.

FIG. 13 is a block diagram illustrating a BS in the wirelesscommunication system according to an exemplary embodiment of the presentinvention.

The BS of FIG. 13 includes on RF receiver 1302, an OFDM demodulator1304, a subcarrier demapper 1306, a plurality of symbol demodulators1308-1 through 1308-N, a plurality of decoders 1310-1 through 1310-N, aplurality of encoders 1312-1 through 1312-N, a plurality of symbolmodulators 1314-1 through 1314-N, a subcarrier mapper 1316, an OFDMmodulator 1318, an RF transmitter 1320, a data buffer 1322, a messageanalyzer 1324, a message generator 1326, a resource allocator 1328, anFA manager 1330, and a communication controller 1332.

The RF receiver 1302 down-converts an RF signal received via an antennato a baseband signal. The OFDM demodulator 1304 divides the basebandsignal output from the RF receiver 1302 on the OFDM symbol basis,eliminates the CP, and restores the frequency-domain complex symbolsusing the FFT operation. The subcarrier demapper 1306 divides thefrequency-domain complex symbols on the FA basis and distributes thecomplex symbols to the symbol demodulators 1308-1 through 1308-N. Thesymbol demodulators 1308-1 through 1308-N each demodulate and convertthe complex symbols to the encoded bit stream. The decoders 1310-1through 1310-N each decode the encoded bit stream.

The encoders 1312-1 through 1312-N each encode the data bit streamtransmitted over the respective FAs. The symbol modulators 1314-1through 1314-N modulate the encoded bit stream transmitted over therespective FAs and convert to complex symbols. The subcarrier mapper1316 maps the complex symbols output from the symbol modulators 1314-1through 1314-N into the frequency domain. Since the symbol modulators1314-1 through 1314-N correspond to the FAs respectively, the subcarriermapper 1316 maps the complex symbols output from the symbol modulators1314-1 through 1314-N to the different FAs. The OFDM modulator 1318converts the complex symbols mapped to the frequency domain totime-domain signals using the IFFT operation, and constitutes OFDMsymbols by inserting the CP. The RF transmitter 1320 up-converts theOFDM symbols to an RF signal and transmits the RF signal via theantenna. The data buffer 1322 temporarily stores the data exchanged withthe MS and outputs the stored data under the control of thecommunication controller 1332.

The message analyzer 1324 analyzes the control message received from theMS, and provides the information obtained from the control message tothe communication controller 1332. For instance, the message analyzer1324 analyzes at least one of the S-FA off request message requesting tostop using the S-FA, the SLP-REQ message including the S-FA off request,an S-FA readiness indicator requesting to resume the suspended S-FA, theS-FA on request message requesting to resume the suspended S-FA, theS-FA readiness indicator informing of the start of the resumption of thesuspended S-FA, the SLP-REQ message requesting the sleep mode entrance,the S-FA off response message informing of the reception of the S-FA offrequest, and the S-FA on response message informing of the reception ofthe S-FA on request.

The message generator 1326 generates the control message transmitted tothe MS. For example, the message generator 1326 generates at least oneof the S-FA off response message informing of the reception of the S-FAuse suspension request, the SLP-RSP message including the S-FA offresponse, an S-FA readiness indicator ACK informing of the reception ofthe S-FA readiness indicator, the S-FA on response message informing ofthe determination result in relation with the S-FA on request, the S-FAoff request message to request to stop using the S-FA, the S-FA onrequest message to request the resumption of the S-FA, and the SLP-RSPmessage including the S-FA off request. Particularly, as generatingeither the S-FA readiness indicator ACK or the S-FA on response message,the message generator 1326 adds the determination result of the BSincluding at least one of the approval of the usage resumption of thesuspended S-FA, the disapproval of the usage resumption of the suspendedS-FA, and the usage allowance of the new FA. As generating either theS-FA off request message or the SLP-RSP message including the S-FA offrequest, the message analyzer 1326 adds at least one of the usesuspension request of the S-FA and the use allowance of the other FA.

The resource allocator 1328 allocates the radio resource to the MS. Inthe resource allocation, the resource allocator 1328 refers to the listof the used FAs of the MS provided from the FA manager 1330. Morespecifically, to allocate the resource to the MS, the resource allocator1328 allocates the resources in the FAs belonging to the list of theused FAs of the MS. The FA manager 1330 manages the list of the used FAsof the accessed MS, and provides the FA use list of the MS to theresource allocator 1328. The FA manager 1330 updates the FA use list ofthe MS under the control of the communication controller 1332.

The communication controller 1332 controls the functions for thecommunication of the BS. The communication controller 1332 controls theoperations and the signalings for the suspension and the resumption ofthe S-FA use. In the various embodiments of the present invention, thedetailed operations of the communication controller 1332 are nowdescribed.

In an exemplary implementation, the when the message analyzer 1324confirms the S-FA off request message, the communication controller 1332controls the FA manager 1330 to exclude the S-FA from the FA use list ofthe MS. The communication controller 1332 controls the message generator1326 to generate the S-FA off response message. Hence, the S-FA offresponse message is transmitted to the BS through the encoders 1312-1through 1312-N, the symbol modulators 1314-1 through 1314-N, thesubcarrier mapper 1316, the OFDM modulator 1318, and the RF transmitter1320. The communication controller 1332 controls the FA manager 1330 toadd the suspended S-FA into the FA use list of the MS. Next, when themessage analyzer 1324 identifies the S-FA readiness indicator, thecommunication controller 1332 determines whether to permit the userequest of the suspended S-FA. When not allowing the use request of thesuspended S-FA, the communication controller 1332 determines whether theuse of other FA may be allowed. The communication controller 1332controls the message generator 1326 to generate the S-FA readinessindicator ACK notifying of its determination result.

In an exemplary implementation, distinctively, when the message analyzer1324 confirms the SLP-REQ message, the communication controller 1332determines whether the SLP-REQ message includes the S-FA off request.When the SLP-REQ message contains the S-FA off request, thecommunication controller 1332 controls the message generator 1326 togenerate the SLP-RSP message including the S-FA off response message.

In an exemplary implementation, distinctively, when the message analyzer1324 identifies the S-FA on request message, the communicationcontroller 1332 determines whether to approve the use request of thesuspended S-FA. When not allowing the use request of the suspended S-FA,the communication controller 1332 determines whether the use of theother FA may be permitted. Next, the communication controller 1332controls the message generator 1326 to generate the S-FA on responsemessage notifying of its determination result. The message analyzer 1324identifies the S-FA readiness indicator, and the communicationcontroller 1332 controls the FA manager 1330 to update the FA use statusinformation of the MS.

In an exemplary implementation, distinctively, when the message analyzer1324 confirms the SLP-REQ message, the communication controller 1332determines whether the SLP-REQ message includes the S-FA off request.When the SLP-REQ message contains the S-FA off request, thecommunication controller 1332 controls the message generator 1326 togenerate the SLP-RSP message including the S-FA off response message.When the message analyzer 1324 confirms the S-FA on request message, thecommunication controller 1332 determines whether to allow the userequest of the suspended S-FA. When not allowing the use request of thesuspended S-FA, the communication controller 1332 determines whether topermit the use of the other FA. Next, the communication controller 1332controls the message generator 1326 to generate the S-FA on responsemessage informing of its determination result. When the message analyzer1324 identifies the S-FA readiness indicator, the communicationcontroller 1332 controls the FA manager 1330 to add the suspended S-FAinto the FA use list of the MS.

In an exemplary implementation, the communication controller 1332determines whether to suspend the use of at least one S-FA. Thesuspension of the at least one S-FA is determined based on the signalstrength measurement value of each S-FA reported from the MS, and theload of each S-FA. Determining to suspend the at least one S-FA, thecommunication controller 1332 determines whether to allow using otherFA. When not allowing use of the other FA, the communication controller1332 controls the message generator 1326 to generate the S-FA requestmessage including the indication information of the suspended S-FA.Conversely, when allowing the use of the other FA, the communicationcontroller 1332 controls the message generator 1326 to generate the S-FArequest message including the indication information of the suspendedS-FA and the newly allowed FA. When the message analyzer 1324 confirmsthe S-FA off response message, the communication controller 1332controls the FA manager 1330 to erase the suspended S-FA from the FA uselist of the MS. Next, when the use resumption of the suspended S-FA isdetermined, the communication controller 1332 controls the messagegenerator 1326 to generate the S-FA on request message including theindication information of the resumed S-FA. When the message analyzer1324 confirms the S-FA on response message and the S-FA readinessindicator, the communication controller 1332 controls the FA manager1330 to add the suspended S-FA into the FA use list of the MS.

In an exemplary implementation, distinctively, when the message analyzer1324 confirms the SLP-REQ message, the communication controller 1332determines whether to permit the sleep mode entrance of the MS andwhether to suspend the use of the at least one S-FA. Upon determining tosuspend the at least one S-FA, the communication controller 1332controls the message generator 1326 to generate the SLP-RSP messageincluding the approval or the disapproval of the sleep mode entrance andthe S-FA off request.

As set forth above, in the broadband wireless communication systememploying the multiple FAs, the power consumption of the MS incurred inusing the S-FA may be reduced by turning on and off the S-FA of the MS.

While the invention has been shown and described with reference tocertain exemplary embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A method for operating a mobile station in awireless communication system using a plurality of Frequency Assignments(FAs), the method comprising: receiving a first Media Access Control(MAC) control message which requests to suspend use of a first Secondary(S)-FA of one or more S-FAs while communicating over a Primary (P)-FAand the one or more S-FAs; communicating over at least the P-FA andexcluding the first S-FA; receiving a second MAC control message whichrequests to resume use of the first S-FA; and communicating over atleast the P-FA and the first S-FA.
 2. The method of claim 1, wherein thefirst MAC control message comprises at least one of indicationinformation of the first S-FA and off duration of the first S-FA,wherein the indication information comprises at least one of frequencyinformation of the first S-FA, an index of the first S-FA, and an S-FAbitmap representing the first S-FA.
 3. The method of claim 2, whereinthe first MAC control message comprises information requesting to use anFA other than the first S-FA and indication information of the other FA.4. The method of claim 1, wherein the first MAC control messagecomprises part of a sleep response message which informs of approval ordisapproval on a sleep mode entrance request of the mobile station. 5.The method of claim 1, further comprising sending a third MAC controlmessage which comprises a response for the request to resume use of thefirst S-FA.
 6. The method of claim 5, further comprising: after sendingthe third MAC control message, preparing to use the first S-FA; and whenthe preparation is completed, sending an S-FA readiness indicator. 7.The method of claim 5, further comprising: before sending the third MACcontrol message, preparing to use the first S-FA; and when thepreparation is completed, sending the third MAC control message torespond to the request to resume use of the first S-FA and to informthat use of the first S-FA may resume.
 8. A mobile station for operatingin a wireless communication system using a plurality of FrequencyAssignments (FAs), the mobile station comprising at least a receiver anda controller, the receiver and the controller configured to: receive, bythe receiver, a first MAC control message which requests to suspend useof a first Secondary (S)-FA of one or more S-FAs while communicatingover a Primary (P)-FA and the one or more S-FAs; and control, by thecontroller, communication over at least the P-FA and excluding the firstS-FA, receive, by the receiver, a second MAC control message whichrequests to resume use of the first S-FA, and control, by thecontroller, communication over at least the P-FA and the first S-FA. 9.The mobile station of claim 8, wherein the first MAC control messagecomprises at least one of indication information of the first S-FA andoff duration of the first S-FA, wherein the indication informationcomprises at least one of frequency information of the first S-FA, anindex of the first S-FA, and an S-FA bitmap representing the first S-FA.10. The mobile station of claim 9, wherein the first MAC control messagecomprises information requesting to use an FA other than the first S-FAand indication information of the other FA.
 11. The mobile station ofclaim 8, wherein the first MAC control message comprises part of a sleepresponse message which informs of approval or disapproval on a sleepmode entrance request of the mobile station.
 12. The mobile station ofclaim 8, wherein the mobile station further comprises a transmitter, thetransmitter configured to: send a third MAC control message whichcomprises a response for the request to resume use of the first S-FA.13. The mobile station of claim 12, wherein the controller and thetransmitter are further configured to: after the third MAC controlmessage is transmitted, prepare, by the controller, to use the firstS-FA; and when the preparation is completed, send, by the transmitter,an S-FA readiness indicator.
 14. The mobile station of claim 12, whereinthe controller and the transmitter are further configured to: beforesending the third MAC control message, prepare, by the controller, touse the first S-FA; and when the preparation is completed, send, by thetransmitter, the third MAC control message to respond to the request toresume use of the first S-FA and to inform that use of the first S-FAmay resume.